1. Field of the Invention
The present invention relates to a lighting system for a vehicle which is constituted to carry out beam irradiation toward the forward road of the vehicle in a predetermined light distribution pattern.
2. Description of the Related Art
As one of the lighting systems for a vehicle besides or a part of a headlamp, which are constituted to carry out beam irradiation toward the forward road of the vehicle, a bending lamp has conventionally been known. The bending lamp is constituted to be turned on when the vehicle turns. Consequently, the visibility of a forward road in a turning direction can be enhanced.
FIG. 9 is a view perspectively showing a light distribution pattern Pa′ formed on the forward road of the vehicle by the beam irradiation of the bending lamp when the vehicle turns in a leftward direction.
FIG. 9(a) shows a state in which the vehicle is making a left turn at a low speed on the forward intersection of the vehicle and FIG. 9(b) shows a state in which the vehicle is turning at medium and high speeds over a left curved road of a highway. In the drawings, a light distribution pattern P(L) shown in a two-dotted chain line indicates a low beam distribution pattern formed by the beam irradiation of a headlamp.
The light distribution pattern Pa′ is wedge-shaped to be expanded in an obliquely downward direction from the vicinity of a hot zone (a region having a high luminous intensity) HZ of the low beam distribution pattern P(L) in a leftward direction and has a hot zone HZ′ in an upper and rightward position. Consequently, the visibility of a forward road in a turning direction is maintained from low speed turning to medium and high speed turning.
However, since the conventional bending lamp is constituted to carry out beam irradiation in a single light distribution pattern Pa′, there is the following problem.
More specifically, the visibility of a road at a short distance is deteriorated due to the brightness of a distant region A2 of the light distribution pattern Pa′ during low speed turning in which the close observation point of a vehicle driver is set into the road at a short distance. On the other hand, the visibility of a distant road is deteriorated due to the brightness of a region A1 on this side of the light distribution pattern Pa′ during medium and high speed turning in which the close observation point of the vehicle driver is set into the distant road.
Such a problem might arise in the same manner also in a lighting system for a vehicle other than the bending lamp.